As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users are information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes, thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems, e.g., computer, personal computer workstation, portable computer, computer server, print server, network router, network hub, network switch, storage area network disk array, RAID disk system and telecommunications switch.
With the present transition to and adoption of the latest very high speed serial technology (e.g., PCI Express—“PCI-E,” Serial Attached SCSI—“SAS,” and fully buffered dual inline memory module ((DIMM)—“FBD”) to information handling system bus designs, noise may induce undesirable signal threshold levels in serial data carrying circuits that should otherwise remain in an idle condition when no data signals are present. In the PCI Express—“PCI-E,” electrical specifications, an electrical idle condition is specified to have alternating current (AC) electrical noise of less than 65 millivolts peak-to-peak. According to the PCI-E specification, any voltage detected at the receiver that is greater than 65 millivolts and less than 170 millivolts, the PCI-E link will exit the electrical idle state. A problem therefore exists when an information handling system operating system (“OS”) is supposed to be in a shutdown condition, but a data receiver does not remain in the electrical idle state, for example a memory controller hub (“MCH”) timeout may occur. If a MCH timeout occurs, the data link will be brought down and cause the MCH to assert a NMI# which may result in the dreaded Windows Operating System “blue screen” and an NMI# Parity Error message. This is because the data receiver (“RX”) never gets the message that it should be in the electrical idle state per a state machine implementation.
To further complicate the RX achieving a desired electrical idle state, the transmitter (“TX”) may generate noise, e.g., up to about 20 millivolts, when in an idle condition, thus the idle noise margin is further diminished, e.g., 65 millivolts (RX)-20 millivolts (TX)=45 millivolts. This 45 millivolt peak-to-peak noise margin also must include noise from within the entire system, e.g., crosstalk, jitter, etc.